On February 27, NHTSA announced a major change to the federal child restraint standard, adopting a 10-year-old into the dummy family and clearly defining lower anchor (LA) weight limits. The addition of the 10-year-old test dummy fulfills a longstanding mandate of Anton’s Law of 2002. It allows NHTSA to expand the applicability of FMVSS 213 to include CRs for use by children up to 80 pounds (previously 65 pounds).

This new rule will not go into effect until February 27, 2014, as NHTSA has determined that CR manufacturers may need two years to adjust to these new requirements.

Although the 10-year-old dummy has been in development since 2000, and its adoption has been a stated goal for NHTSA over the past decade, it has been on a long journey to this final rule. The original Notice of Proposed Rulemaking (NPRM) was issued in 2005, but major concerns from the industry prompted supplemental NPRMs in 2008 and 2010.

One serious concern cited by CR manufacturers about the 10-year-old was the positioning procedure for the dummy in order to get reliable test results. After much deliberation and testing of various procedures, the final rule adopts the procedure put forth by the University of Michigan Transportation Research Institute (UMTRI) for both the 6-year-old (HIII-6C) and the 10-year-old dummies (HIII-10C). (The HIII-10C also will include a pelvis-positioning pad as part of the procedure.)

Also of concern during the long process of 213 revision is the biofidelity of the HIII-10C with respect to head injury criteria (HIC). In particular, manufacturers noted that the dummy has a tendency to have significant chin-to-chest impacts leading to unrealistically high HIC scores. Since there is no evidence to suggest that this type of injury mechanism exists for real children in crashes, and an engineering solution to the problem has not been developed, NHTSA agreed that HIC criteria will not apply to CRs tested with the new HIII-10C. However, NHTSA ruled that the HIII-10C did provide good biofidelity for excursion and chest acceleration measurements, so criteria for these requirements will apply.

With respect to LA weights, NHTSA expressed agreement with commenters representing the vehicle manufacturers who argued that anchor strength limits must take into account the weights of both the child and CR. Settling on this approach for labeling of anchor weight maximums will fulfill a NHTSA goal of reducing consumer confusion and misuse by stating a clear child-weight limit on each CR for using the lower anchors for installation.

Tether anchor (TA) weight limits are not specified by this rule. NHTSA made a point to separate TAs from the LAs in specifying these LA limits, and the ruling pointedly refrains from imposing a weight limit on tether use. As stated by NHTSA in the final rule, “A significant portion of the harm to children resulting from motor vehicle crashes could be prevented by the tether.” Therefore, the agency determined that it will test harness-equipped CRs for use above 65 pounds with and without tether attachment when testing with the HIII-10C (installed with a seat belt). No consumer warning to curtail tether use at a given weight will be required. Caregivers should therefore continue to consult the vehicle manufacturers to determine tether anchor weight limits. These TA limits are also published in the 2011 LATCH Manual*.

*(UPDATE: Always consult the most current LATCH Manual for LATCH weight limits, now the 2013 edition. Order Here)

Key details of the new rule include:

The 77-pound, 10-year-old dummy will be used for testing of CRs intended for children from 65 to 80 pounds. CRs for use from 50 to 65 pounds will continue to be tested with the 51-pound, 6-year-old dummy for performance and with the 6-year-old weighted to 62 pounds (clothed) for structural integrity.

When the dummy PLUS CR weigh more than 65 lbs, harness-equipped CRs will be tested only when installed with a seat belt (not with the lower anchors). NHTSA explains in the ruling that this is because FMVSS 225 was not developed with the expectation that CRs would be used for weights higher than this. However, CRs tested with the new 10-year-old dummy will be required to pass head excursion requirements in both tethered and untethered scenarios when installed with the seat belt.

Since some CRs with higher harness weight limits will not be tested to the CR’s upper weight limit when installed with lower anchors, NHTSA has further ruled that a consumer warning label must appear on all such CRs regarding the weight limit for using the lower anchors. This advice also will appear in the CR owner’s manual. The required warning label will state a maximum child weight for lower anchor use. The CR manufacturer will calculate the weight limit by subtracting the CR weight from 65 pounds. In other words, each CR model will have a specific maximum child-weight limit for using the LAs that’s dependent upon the weight of the CR, so that the limit for installing with LAs takes into account the combined child plus CR weight. The standard also clarifies that these weight limits do not apply to LA installations for boosters or CRs used in booster mode.